Thermodynamic properties of solution in 3-methylsydnone (3MS) and of adsorption at the nitrogen/3MS interface were gas chromatographically measured for a group of fifteen hydrocarbons at infinite dilution conditions. Retention volumes were measured at five temperatures within the range 37-52 degrees C in six columns containing different loadings of 3MS on Chromosorb P AW, Partition and adsorption coefficients were calculated and from their temperature dependence the corresponding enthalpies were obtained, although with considerable error; infinite dilution activity coefficients of the hydrocarbons in the bull; and in the surface phases demonstrated a strong correlation. Bulk activity coefficients in 3MS were very much smaller than those previously measured for the same solutes in formamide (FA) and. in ethyleneglycol (EG), and were also smaller than what could be predicted on account of 3MS cohesive energy density as estimated from the quotient sigma/nu(1/3) (sigma, surface tension; nu, molar volume), There was not such a large difference between the surface activity coefficients in the three solvents; furthermore, the quotients (sur-Face activity coefficient/bulk activity coefficient) for a given salute in 3MS were twice as large as in FA and about three times larger than in EG, These results ma!ie evident the difficulties inherent in the prediction of surface phase properties from those ire the bulk and cast doubts on the pertinency of employing the surface tension to compare cohesive energy densities of polar solvents with important chemical differences.